This project examined multiple aspects of the reproductive biology of the wetland invasive species, purple loosestrife (<i>Lythrum salicaria</i> L.), in central Saskatchewan. An examination of insect taxa visiting the three floral morphs of <i>Tristylous</i> L. <i>salicaria</i>, as well as a ranking of the pollination efficiency of individual insect species, an apparent first for L salicaria, was undertaken. Surface features of the floral nectary of L. <i>salicaria</i>, as well as floral nectar secretion dynamics, were also investigated. This project also re-visited some of the previous work done on this invasive species, including various floral organ morphometrics in relation to heterostyly, and aspects of the tristylous breeding system including self-fertilization, and fertilization potential of both illegitimate pollination and legitimate pollination.<p>The trimorphic nature of the sexual floral organs of L. <i>salicaria</i> were well defined in Saskatchewan. Significant differences in length (long-, intermediate- and short-style lengths) exist between all three floral morphs. Lengths of the staminal filaments (long, intermediate, and short) were also significantly different. Also the floral nectary in L. <i>salicaria</i> is located in a depression formed at the interface of the hypanthium and the gynoecium. Several stomata are located at regular intervals along the nectary surface, and may constitute the escape route for floral nectar. No morphological differences in nectary structure were apparent among the three floral morphs.<p>Nectar secretion dynamics of L. <i>salicaria</i> were examined between the three floral morphs throughout two summer days in 2006. Peak average nectar volumes and nectar sugar quantities were detected at 3:00 pm, and, interestingly, no significant differences were detected between floral morphs, in accordance with nectary morphology. The estimated secretion rates for L. <i>salicaria</i> ranged from 61 83 µg of nectar sugar per flower per hour.<p>Hand-pollination experiments carried out over the summers of 2006 and 2007 at three field sites in and around Saskatoon have verified the strong self-incompatibility in the breeding system of this tristylous species. Intramorph pollination, using illegitimate pollen, did not result in fertilisation, whereas legitimate hand-pollination experiments yielded multiple pollen tubes at the style base, without exception.<p><i>Lythrum salicaria</i> in central Saskatchewan was visited by several bee taxa including honeybees (<i>Apis mellifera</i> L.), bumblebees (Bombus spp.), leafcutter bees (Megachile spp.), and sweat bees (Lasioglossum spp.). A single visit by <i>Anthophora furcata</i> (Panzer) was also recorded in 2007. Generally, bee visits led to high levels of pollination success as determined by fluorescence microscopy of pollen tubes following single insect visits to previously-unvisited flowers. However, most visits by hoverflies (Syrphidae) were non-pollinating. Visits by Pieris rapae (L.), yellowjacket wasps (Vespidae) and some non-syrphid flies (Diptera) also yielded no pollen tubes at the style base.<p>A study of the ultrastructure and development of the floral nectary of the purple loosestrife cultivar Morden Gleam (<i>Lythrum virgatum</i> L. x L. alatum Pursh.) showed that starch build up in pre-secretory nectary tissues declined throughout secretion, and is virtually absent in post-secretory nectary tissues. The lack of a direct vascular supply to the floral nectary suggests that the starch breakdown products likely make up most of the floral nectar carbohydrates. Surface features of the floral nectary in Morden Gleam closely resembled those of L. salicaria, located in the valley formed between the hypanthium and gynoecium. Nectary stomata, occasionally in pairs, likely serve as outlets for nectar in this cultivar.

This project examined multiple aspects of the reproductive biology of the wetland invasive species, purple loosestrife (<i>Lythrum salicaria</i> L.), in central Saskatchewan. An examination of insect taxa visiting the three floral morphs of <i>Tristylous</i> L. <i>salicaria</i>, as well as a ranking of the pollination efficiency of individual insect species, an apparent first for L salicaria, was undertaken. Surface features of the floral nectary of L. <i>salicaria</i>, as well as floral nectar secretion dynamics, were also investigated. This project also re-visited some of the previous work done on this invasive species, including various floral organ morphometrics in relation to heterostyly, and aspects of the tristylous breeding system including self-fertilization, and fertilization potential of both illegitimate pollination and legitimate pollination.<p>The trimorphic nature of the sexual floral organs of L. <i>salicaria</i> were well defined in Saskatchewan. Significant differences in length (long-, intermediate- and short-style lengths) exist between all three floral morphs. Lengths of the staminal filaments (long, intermediate, and short) were also significantly different. Also the floral nectary in L. <i>salicaria</i> is located in a depression formed at the interface of the hypanthium and the gynoecium. Several stomata are located at regular intervals along the nectary surface, and may constitute the escape route for floral nectar. No morphological differences in nectary structure were apparent among the three floral morphs.<p>Nectar secretion dynamics of L. <i>salicaria</i> were examined between the three floral morphs throughout two summer days in 2006. Peak average nectar volumes and nectar sugar quantities were detected at 3:00 pm, and, interestingly, no significant differences were detected between floral morphs, in accordance with nectary morphology. The estimated secretion rates for L. <i>salicaria</i> ranged from 61 83 µg of nectar sugar per flower per hour.<p>Hand-pollination experiments carried out over the summers of 2006 and 2007 at three field sites in and around Saskatoon have verified the strong self-incompatibility in the breeding system of this tristylous species. Intramorph pollination, using illegitimate pollen, did not result in fertilisation, whereas legitimate hand-pollination experiments yielded multiple pollen tubes at the style base, without exception.<p><i>Lythrum salicaria</i> in central Saskatchewan was visited by several bee taxa including honeybees (<i>Apis mellifera</i> L.), bumblebees (Bombus spp.), leafcutter bees (Megachile spp.), and sweat bees (Lasioglossum spp.). A single visit by <i>Anthophora furcata</i> (Panzer) was also recorded in 2007. Generally, bee visits led to high levels of pollination success as determined by fluorescence microscopy of pollen tubes following single insect visits to previously-unvisited flowers. However, most visits by hoverflies (Syrphidae) were non-pollinating. Visits by Pieris rapae (L.), yellowjacket wasps (Vespidae) and some non-syrphid flies (Diptera) also yielded no pollen tubes at the style base.<p>A study of the ultrastructure and development of the floral nectary of the purple loosestrife cultivar Morden Gleam (<i>Lythrum virgatum</i> L. x L. alatum Pursh.) showed that starch build up in pre-secretory nectary tissues declined throughout secretion, and is virtually absent in post-secretory nectary tissues. The lack of a direct vascular supply to the floral nectary suggests that the starch breakdown products likely make up most of the floral nectar carbohydrates. Surface features of the floral nectary in Morden Gleam closely resembled those of L. salicaria, located in the valley formed between the hypanthium and gynoecium. Nectary stomata, occasionally in pairs, likely serve as outlets for nectar in this cultivar.

Les insectes contribuent à la pollinisation de 70% des espèces cultivées aujourd’hui à travers le monde. Avec l’intensification de l’agriculture au début du XXème siècle, les agriculteurs se sont mis à introduire des colonies d’abeilles mellifères dans leurs cultures entomophiles pour assurer le service de pollinisation. Avec la reconnaissance croissante du rôle majeur joué par les insectes sauvages dans la pollinisation des cultures, le concept de pollinisation intégrée des cultures a récemment vu le jour, encourageant à combiner insectes pollinisateurs introduits et sauvages en adaptant les pratiques agricoles pour assurer une pollinisation durable des cultures. Mais l’introduction d’insectes pollinisateurs d’élevage est une pratique encore très empirique qui manque de références techniques pour pouvoir être mise en œuvre avec précision. L’objectif général de cette thèse était de fournir des éléments pour mettre au point une méthode objective pour définir la charge en unités opérationnelles d’abeilles mellifères à introduire par unité de surface de culture cible pour complémenter la faune pollinisatrice sauvage pour que la pollinisation ne soit pas un facteur de production limitant.Nous avons travaillé sur une lignée mâle fertile et une lignée mâle stérile de colza (Brassica napus L.), les productions de semence hybride dépendant entièrement des insectes pour la pollinisation chez cette espèce. Nous avons pu déterminer (i) le nombre minimum de grains de pollen viables devant être déposés par stigmate pour que la grenaison puisse être complète en fonction de la température, (ii) la durée après anthèse pendant laquelle le pollen doit être déposé sur le stigmate pour que la grenaison puisse être complète en fonction de la température, (iii) la durée pendant laquelle une fleur sécrète du nectar en fonction de la température pour chacune des deux lignées, et (iv) la vitesse de cette sécrétion nectarifère en fonction de la température pour chacune des deux lignées. Nous avons également validé une méthode d’évaluation rapide de la taille des cheptels d’abeilles mellifères introduits dans les cultures entomophiles, couramment utilisée dans certains pays, en tenant compte de la température.A partir de ces éléments, nous avons proposé d’introduire les concepts d’offre et de demande en pollinisation d’une culture cible, afin de quantifier les déficits de pollinisation et le nombre d’insectes pollinisateurs à introduire pour compléter ces déficits. Ces premiers éléments fournissent une base pour construire un modèle mécaniste de gestion intégrée de la pollinisation, pour prédire le nombre d’insectes pollinisateurs à introduire dans une culture étant donné son contexte climatique, paysager et variétal. / Insects contribute to the pollination of 70% of the species cultivated today around the world. With the agriculture intensification in the early twentieth century, farmers began to introduce honey bees colonies into their entomophilous crops to provide pollination service. With the growing recognition of the major role played by wild insects in crop pollination, the concept of integrated crop pollination recently emerged, encouraging the combination of introduced and wild pollinating insects by adapting agricultural practices to ensure sustainable pollination of crops. But the introduction of managed pollinating insects is still an empirical practice that lacks technical references to be implemented with precision. The general objective of this thesis was to provide elements to develop an objective method to define the operational unit load of honey bees to be introduced per unit area of target crop to complement wild pollinating fauna so that pollination is not a limiting factor for production.We worked on a male fertile and a male sterile oilseed rape (Brassica napus L.) lines, hybrid seed productions being entirely dependent on insects for pollination in this species. We were able to determine (i) the minimum number of viable pollen grains to be deposited on stigma so that seed set was complete depending on the temperature, (ii) the duration after anthesis during which the pollen must be deposited on the stigma so that seed set was complete depending on the temperature, (iii) the length of time a flower secretes nectar as a function of temperature for each of the two lines, and (iv) the rate of this nectar secretion as a function of temperature for each of the two lines. We also validated a method for rapid assessment of the size of honey bee stocking rate introduced into entomophilous crops, commonly used in some countries, taking into account temperature.From these elements, we proposed to introduce the concepts of supply and demand in pollination of a target crop, in order to quantify the pollination deficits and the number of pollinating insects to introduce to complete these deficits. These first elements provide a basis for constructing a mechanistic model of integrated pollination management, to predict the number of pollinating insects to be introduced into a crop given its climatic, landscape and varietal context.

The main objective of this research project was to study the growth and development of the floral nectar spur of Centranthus ruber (L.) DC. Nectar spurs are tubular floral outgrowths, generally derived from the perianth organs, which typically contain secreted floral nectar. The morphological characteristics of the spur, particularly the length, determine which floral visitors will be able to access the nectar reward pooled at the spur tip. Therefore, nectar spurs are ecologically important for the development of specialised pollinator interactions and have been demonstrated to act as key innovations in the evolution of some taxa. Morphological and anatomical characteristics of the spur and floral nectary were investigated using light and scanning electron microscopy. Ultrastructural features of the nectar spur, particularly the floral nectary within, were assessed using transmission electron microscopy. Nectar in C. ruber is produced by a trichomatous nectary which runs along the entire, inner abaxial surface of the spur. The nectary is aligned with the single vascular bundle which runs along the abaxial side of the spur, through the sub-nectary parenchyma, and back up the adaxial side. The secretory trichomes are unicellular and, in late development, they develop a thick layer of secondary wall ingrowths which vastly increases the surface area of the plasma membrane for nectar secretion. Elongate, non-secretory trichomes occupy the entire remaining circumference of the spur’s inner epidermis, but their density is reduced compared to the secretory trichomes. The cellular basis for spur growth is poorly characterized in the literature. Until recently, it was assumed that all nectar spurs grow by the constant production of new cells via up to three potential meristematic regions (the meristem hypothesis, Tepfer 1953). The cellular basis for spur growth in C. ruber was investigated by cell file counts and cell length and width measurements along the lateral side of nectar spurs in each of the developmental stages. DAPI stained spurs were also examined with Confocal/Apotome microscopy to determine the timing and position of cell division activity throughout spur development. It was determined that elongation of the spur epidermal cells contributes much more to spur growth than cell division. In early development, division is the primary driver of spur growth and the cells are isotropic. However, as development progresses, cell division activity slows down and the spur cells become increasingly anisotropic until anthesis. The patterns of nectar secretion were determined by assessing the volume, solute concentration and carbohydrate composition of the nectar throughout flowering phenology in two C. ruber plants. Nectar volumes and solute amounts rose initially, followed by an eventual decline in both as phenology progressed towards senescence. Because this study was conducted on greenhouse grown plants, it can be assumed that nectar was not removed by insects, suggesting that it is likely reabsorbed following secretion. High performance liquid chromatography (HPLC) analysis determined that C. ruber's nectar is sucrose dominant and that nectar composition remains stable following anthesis throughout floral phenology.